head bolt stretch is this normal or do I have to start over

[84Westfalia]

I'm doing a head gasket job and I just torqued the new head bolts as per the Bentley. When I was giving the first 1/4 turn after the second torque sequence, it felt like one bolt let go, but it did not strip. I then proceeded to do the second 1/4 turn and several more did the same thing, like they lost torque but they were not stripped. is this normal? I have a kind of sick feeling like I just stretched the bolts beyond their capacity. I cleaned the bolt holes with brake cleaner and lightly lubed the bolts with WD40 before starting.

it's a on 1990 cabriolet.

Thanks

[gtidaddy]

I'm doing a head gasket job and I just torqued the new head bolts as per the Bentley. When I was giving the first 1/4 turn after the second torque sequence, it felt like one bolt let go, but it did not strip. I then proceeded to do the second 1/4 turn and several more did the same thing, like they lost torque but they were not stripped. is this normal? I have a kind of sick feeling like I just stretched the bolts beyond their capacity. I cleaned the bolt holes with brake cleaner and lightly lubed the bolts with WD40 before starting.

it's a on 1990 cabriolet.

Thanks

you do know vw headbolts are a onetime use.

[84Westfalia]

yes I used new head bolts. They were Victor Reinz bolts. The directions with the Rein head gasket said to lightly oil the bolts and the holes. I've stopped puttign anything on to get some opinions on if this is normal for the torque to seem to let go...but I've never torqued torque to yield bolts before.

[gtidaddy]

i have never used those bolts.i get my head bolts from the dealer.
as for bolt lube i either use engine assembly lube or engine oil.
as far as what you encountered don't think i have experience that, maybe someone else can chime in

[briano1234]

I would place a torque wrench on it and if it is still at the max, I would bet that you are ok on it.
I personally never have seen that issue.

[fquint]

I've done a few 1.8 head gasket jobs and what you are describing sounds odd to say the least.

I doubt that your head bolts stretched. If you still have the old head bolts, compare the new ones side by side to see if there is any difference. You can also try putting the old head bolts in and torquing them down. If they seem to torque properly then its likely you have an issue with your new head bolts and you should try replacing them. If your old head bolts do the same then you may have an issue with the threads in the block.

If you are not certain that your head has the proper torque I recommend that you take the car to a trusted machine shop and have them inspect the head bolt threads in the block for damage.

Even if you spend a couple hundred bucks in towing it's a lot cheaper than the damage you will cause if you run the car with an improperly torqued head.

[speedtek40]

They're probably fine......that second 1/4 turn is unnerving at best (I found anyways....lol). After cranking the **** out of your bolts, they ask you do some extra. As already mentioned, check your torque with the wrench and if it's good, you're fine........don't undo them or you will be starting from scratch...new bolts...new gasket.....

[84Westfalia]

[QUOTE=speedtek40;78580004that second 1/4 turn is unnerving at best (I found anyways....lol). After cranking the **** out of your bolts, they ask you do some extra. As already mentioned, check your torque with the wrench and if it's good, you're fine........don't undo them or you will be starting from scratch...new bolts...new gasket.....[/QUOTE]

Yes I was thinking the same thing as I was using my power bar to give them that first 1/4 turn thinking holly crap this is really tight, then the 7th bolt felt like it let go of something and I got that sick feeling like I just stripped the case. On the 2nd 1/4 turn a few more did the same thing, but not all of them and the #7 bolt felt the same and did not seem to get tighter, but was still tight.

I'm thinking new studs, gasket, exhaust manifold gasket (+ clean all the RTV from the exhaust flange) but what concerns me most is I don't think I did anything wrong...except maybe use WD40 instead of oil and that I might be in the same place again after doing it all over...

Anyway, I'll check the torque to see what I get and report back after work today.

Thanks everyone

[84Westfalia]

I have a Mastercraft digital torque wrench and here are my readings in ft. lb. The bolt number are as per the Bentley torque sequence.

I took 2 readings for each bolt with the first torque value being the first reading:

Bolt 1 70 ft. lb. 68 ft. lb.
Bolt 2 51 ft. lb. 53 ft. lb.
Bolt 3 61 ft. lb. 62 ft. lb.
Bolt 4 63 ft. lb. 60 ft. lb.
Bolt 5 92 ft. lb. 92 ft. lb.
Bolt 6 58 ft. lb. 56 ft. lb.
Bolt 7 57 ft. lb. 55 ft. lb.
Bolt 8 56 ft. lb. 51 ft. lb.
Bolt 9 64 ft. lb. 61 ft. lb.
Bolt 10 57 ft. lb. 54 ft. lb.

Bolt number 5 was stiff and creaked when it finally moved.

So....what do you think??? It would have been nice to keep track of the ones that "let go" yesterday. I'm guessing #5 did not let go.

[84Westfalia]

So i've been googling and found this site:

http://www.rv8.ch/article.php/20051227112926716

It sounds like what I experienced with the "lettign go feeling" is the bolts going from the elastic to the plactic stage. I still can't figure out if it is normal for this to happen with these bolts or not . Once I went past the elastic stage they turned but did not seem to get tighter which corresponds to the plastic stage. It kind of makes sense that they were stretching but not getting tighter by the way they felt. I keep flip flopping on what to and my wife is getting impatient to have her car back.

[chickenfriend]

It is important to understand this is a precision process.

My limited experience with the TTY headbolts is that I feel the my applied torque level-out at the very end of the final turn sequence.

"Leveling-out" does not mean the turning gets easier, it means you are not feeling the ever increasing resistance of the bolt getting tighter. This is a critical distinction.

The feeling you have is that the bolt is getting ready to snap, so that makes you uneasy, since it goes against your instinct. However, this is normal behavior for a stretch bolt.

How do you make sure you will get to the bolts to this point, not before and not beyond where they begin to weaken?

First, the headbolt holes need to be chased with a thread restorer. That is ideal. It you don't have a thread restorer, then you can use a bottoming tap. If you don't have a bottoming tap, then take a regular tap and cut off the tapered end with a silicon carbide cutting wheel on a dremel tool.

Clean the debris from the holes with compressed air.

If you do not chase the bolt holes, friction will cause the bolts to be under-torqued, and since the stretch part is at the very end of the sequence (I want to say about the last 10 degrees), you may not even get to the stretch phase.


Normally, the headbolts are lightly pre-oiled. Do NOT use anything else on the bolts or holes. The sequence is calibrated for the lubricant on the bolts. If the bolts are bone dry, use a light-grade machine oil, certainly no anti-seize.

Your torque wrench must be checked for calibration. You might be able to find a tool dealer or shop that has a tester. Learn how to use your torque wrench properly and don't loan it to anyone. Back off the setting collar to the lower end of the scale before putting it into storage.

Use a long-handled breaker bar for the final degree turns. You need that leverage to help with the control and to keep your rotator cuff from being pulled. 2 feet would be a good length.

The advantage of the TTY bolt is even clamping pressure which cannot be obtained with non-stretch bolts.

The only bolt better than a TTY is a stud. It is stronger, has even clamping pressure, and is reuseable. The disadvantage is the extra cost over TTY bolts.

[84Westfalia]

Update:

I took the head off again and started fresh. This time I chased the threads in the block with a M11 x 1.5 bottom tap, I cleaned the holes out with brake cleaner and then compresses air. I used motor oil on the threads and under the head bolt washers. I marked the head bolt heas with a marker so I could see when I rotated them 90 degrees, I had bought a tool to measure the degree the bolts were turning as I was tightening but it did not work very well so I'm glad I used the marker as a back up. I followed the torque sequence outlined in the Bentley and I did not feel any of the bolts "let go" or streatch like they did in my first attempt. Before starting I compared the lenght of the new bolts to the "old" new one from my first attempt and they were stretched like they were supposed to, but probably not to spec.

[mk3_vdub]

I usually use the arp assembly lube or just a bunch of oil.

I would spend another $30 in head bolts and start over. take one of the old ones and cut some notches down it to make a tap, and run it through the threads to clean them out.

most likely its some crap in the threads or not enough lubricant.

the giving way is normal. the graph below should illustrate better.

when looking at the stress/strain curve, you move into the plastic region after passing the elastic limit at the top of the linear elastic region (youngs modulus of elasticity) and go into the yielding region.

when you torque a one time use bolt down, you are tightening it into the strain hardening region so the material gets closer to its ultimate stress. after that it starts to neck then fracture.

if you somehow managed to torque it past its ultimate stress you would probably be able to feel it start to neck, but I've NEVER seen a head bolt do that. you'd probably rip threads out of the block before you could get it that tight.



this is also why stretch bolts can't be reused. because once its in the plastic region, when the bolt is unloaded it follows the same slope as the modulus of elasticity down from the point on the graph where it was loaded to and the bolts length is permanently deformed.

side by side you probably won't be able to tell any difference, but if you pull out a micrometer you will.

[mk3_vdub]

lol sorry I posted before I read to the bottom of the thread and saw you've fixed it